Thank you for your question. Our bath fans are designed to be installed with the bottom of the can flush with the finished side of the dry wall. When installed incorrectly the grille will not attach properly. Correct install is to: Squeeze grille springs together and insert into slots in motor plate. Push grille up against ceiling. Grille used on models (663,670,671, 675.688 and 689).
If you need additional assistance please contact Technical Service at 1-800-637-1453.